The current 'group chats' (MUC/Multi User Chat) in XMPP are actually just IRC chatrooms with XMPP behind it, which means they're really dumb and people just use IRC for chatroom communications instead. However, there is something in the works called 'MIX', which is what most people would think of when they think of group chats. I won't go into details because I'm not an expert on the subject, but essentially, MUC (current) is crap, MIX (future) is good. We aren't in the future yet.

No, proper offline messaging (so messaging that actually works) is on the todo list, as I mentioned earlier in the thread.

But still, if you want communication between different protocols, someone will always have to be responsible for the different bridges between those protocols, to accomodate any changes. Usually, a protocol doesn't change very often, but when it does the changes tend to be quite large, so if no one or not enough people are around to work on that bridge, no one will be able to cross it anymore.